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MDOM::Element(3) User Contributed Perl Documentation MDOM::Element(3)
 

MDOM::Element - The abstract Element class, a base for all source objects

  MDOM::Element is the root of the PDOM tree

The abstract "MDOM::Element" serves as a base class for all source-related objects, from a single whitespace token to an entire document. It provides a basic set of methods to provide a common interface and basic implementations.

Because we treat whitespace and other non-code items as Tokens (in order to be able to "round trip" the MDOM::Document back to a file) the "significant" method allows us to distinguish between tokens that form a part of the code, and tokens that aren't significant, such as whitespace, POD, or the portion of a file after (and including) the "__END__" token.
Returns true if the Element is significant, or false it not.

Accessor for current line number.

The "class" method is provided as a convenience, and really does nothing more than returning "ref($self)". However, some people have found that they appreciate the laziness of "$Foo->class eq 'whatever'", so I have caved to popular demand and included it.
Returns the class of the Element as a string

The "tokens" method returns a list of MDOM::Token objects for the Element, essentially getting back that part of the document as if it had not been lexed.
This also means there are no Statements and no Structures in the list, just the Token classes.

For any "MDOM::Element", the "content" method will reconstitute the base code for it as a single string. This method is also the method used for overloading stringification. When an Element is used in a double-quoted string for example, this is the method that is called.
WARNING:
You should be aware that because of the way that here-docs are handled, any here-doc content is not included in "content", and as such you should not eval or execute the result if it contains any MDOM::Token::HereDoc.
The MDOM::Document method "serialize" should be used to stringify a PDOM document into something that can be executed as expected.
Returns the basic code as a string (excluding here-doc content).

Elements themselves are not intended to contain other Elements, that is left to the MDOM::Node abstract class, a subclass of "MDOM::Element". However, all Elements can be contained within a parent Node.
If an Element is within a parent Node, the "parent" method returns the Node.

For a "MDOM::Element" that is contained (at some depth) within a MDOM::Statment, the "statement" method will return the first parent Statement object lexically 'above' the Element.
Returns a MDOM::Statement object, which may be the same Element if the Element is itself a MDOM::Statement object.
Returns false if the Element is not within a Statement and is not itself a Statement.

For a "MDOM::Element" that is contained within a PDOM tree, the "top" method will return the top-level Node in the tree. Most of the time this should be a MDOM::Document object, however this will not always be so. For example, if a subroutine has been removed from its Document, to be moved to another Document.
Returns the top-most PDOM object, which may be the same Element, if it is not within any parent PDOM object.

For an Element that is contained within a MDOM::Document object, the "document" method will return the top-level Document for the Element.
Returns the MDOM::Document for this Element, or false if the Element is not contained within a Document.

All MDOM::Node objects (specifically, our parent Node) contain a number of "MDOM::Element" objects. The "next_sibling" method returns the "MDOM::Element" immediately after the current one, or false if there is no next sibling.

As per the other 's' methods, the "snext_sibling" method returns the next significant sibling of the "MDOM::Element" object.
Returns a "MDOM::Element" object, or false if there is no 'next' significant sibling.

All MDOM::Node objects (specifically, our parent Node) contain a number of "MDOM::Element" objects. The "previous_sibling" method returns the Element immediately before the current one, or false if there is no 'previous' "MDOM::Element" object.

As per the other 's' methods, the "sprevious_sibling" method returns the previous significant sibling of the "MDOM::Element" object.
Returns a "MDOM::Element" object, or false if there is no 'previous' significant sibling.

As a support method for higher-order algorithms that deal specifically with tokens and actual Perl content, the "first_token" method finds the first MDOM::Token object within or equal to this one.
That is, if called on a MDOM::Node subclass, it will descend until it finds a MDOM::Token. If called on a MDOM::Token object, it will return the same object.
Returns a MDOM::Token object, or dies on error (which should be extremely rare and only occur if an illegal empty MDOM::Statement exists below the current Element somewhere.

As a support method for higher-order algorithms that deal specifically with tokens and actual Perl content, the "last_token" method finds the last MDOM::Token object within or equal to this one.
That is, if called on a MDOM::Node subclass, it will descend until it finds a MDOM::Token. If called on a MDOM::Token object, it will return the itself.
Returns a MDOM::Token object, or dies on error (which should be extremely rare and only occur if an illegal empty MDOM::Statement exists below the current Element somewhere.

As a support method for higher-order algorithms that deal specifically with tokens and actual Perl content, the "next_token" method finds the MDOM::Token object that is immediately after the current Element, even if it is not within the same parent MDOM::Node as the one for which the method is being called.
Note that this is not defined as a MDOM::Token-specific method, because it can be useful to find the next token that is after, say, a MDOM::Statement, although obviously it would be useless to want the next token after a MDOM::Document.
Returns a MDOM::Token object, or false if there are no more tokens after the Element.

As a support method for higher-order algorithms that deal specifically with tokens and actual Perl content, the "previous_token" method finds the MDOM::Token object that is immediately before the current Element, even if it is not within the same parent MDOM::Node as this one.
Note that this is not defined as a MDOM::Token-only method, because it can be useful to find the token is before, say, a MDOM::Statement, although obviously it would be useless to want the next token before a MDOM::Document.
Returns a MDOM::Token object, or false if there are no more tokens before the "Element".

As per the Clone module, the "clone" method makes a perfect copy of an Element object. In the generic case, the implementation is done using the Clone module's mechanism itself. In higher-order cases, such as for Nodes, there is more work involved to keep the parent-child links intact.

The "insert_before" method allows you to insert lexical perl content, in the form of "MDOM::Element" objects, before the calling "Element". You need to be very careful when modifying perl code, as it's easy to break things.
In its initial incarnation, this method allows you to insert a single Element, and will perform some basic checking to prevent you inserting something that would be structurally wrong (in PDOM terms).
In future, this method may be enhanced to allow the insertion of multiple Elements, inline-parsed code strings or MDOM::Document::Fragment objects.
Returns true if the Element was inserted, false if it can not be inserted, or "undef" if you do not provide a MDOM::Element object as a parameter.

The "insert_after" method allows you to insert lexical perl content, in the form of "MDOM::Element" objects, after the calling "Element". You need to be very careful when modifying perl code, as it's easy to break things.
In its initial incarnation, this method allows you to insert a single Element, and will perform some basic checking to prevent you inserting something that would be structurally wrong (in PDOM terms).
In future, this method may be enhanced to allow the insertion of multiple Elements, inline-parsed code strings or MDOM::Document::Fragment objects.
Returns true if the Element was inserted, false if it can not be inserted, or "undef" if you do not provide a MDOM::Element object as a parameter.

For a given "MDOM::Element", the "remove" method will remove it from its parent intact, along with all of its children.
Returns the "Element" itself as a convenience, or "undef" if an error occurs while trying to remove the "Element".

For a given "MDOM::Element", the "remove" method will remove it from its parent, immediately deleting the "Element" and all of its children (if it has any).
Returns true if the "Element" was successfully deleted, or "undef" if an error occurs while trying to remove the "Element".

Although some higher level class support more exotic forms of replace, at the basic level the "replace" method takes a single "Element" as an argument and replaces the current "Element" with it.
To prevent accidental damage to code, in this initial implementation the replacement element must be of the same class (or a subclass) as the one being replaced.

If the Element exists within a MDOM::Document that has indexed the Element locations using "MDOM::Document::index_locations", the "location" method will return the location of the first character of the Element within the Document.
Returns the location as a reference to a three-element array in the form "[ $line, $rowchar, $col ]". The values are in a human format, with the first character of the file located at "[ 1, 1, 1 ]".
The second and third numbers are similar, except that the second is the literal horizontal character, and the third is the visual column, taking into account tabbing.
Returns "undef" on error, or if the MDOM::Document object has not been indexed.

It would be nice if "location" could be used in an ad-hoc manner. That is, if called on an Element within a Document that has not been indexed, it will do a one-off calculation to find the location. It might be very painful if someone started using it a lot, without remembering to index the document, but it would be handy for things that are only likely to use it once, such as error handlers.

See the support section in the main module.

Adam Kennedy <adamk@cpan.org>

Copyright 2001 - 2006 Adam Kennedy.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
The full text of the license can be found in the LICENSE file included with this module.
2014-11-19 perl v5.28.1

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